An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so light can pass. In fiber optic terminations, glass or plastic fibers are bonded to precision ferrule connectors (“FC”s), also described as fiber channel connectors, and polished for splitting or connecting two fibers together.
It is desirable to increase the bandwidth of a single FC by integrating as many fiber optic cables in the FC as possible. However, the ability to integrate a large number of fiber optic cables within a single FC is typically limited by the physical design structure of the FC.
Mechanical transfer (“MT”) ferrules are particularly susceptible to this issue. An MT Ferrule is a multi-fiber ferrule in which fiber alignment is dependent on the eccentricity and pitch of the fiber and alignment pin holes. The alignment is dictated by the alignment pins during mating. The critical elements for fiber alignment are the ability to hold extreme tolerances for precision during the molding process and the shape, tolerances and material composition of the alignment pins.
In particular, in the VMEbus International Trade Association (VITA) 66.4 Fiber-Optic Connectors for use with MT Ferrules system, the ability to achieve a high bandwidth connection utilizing a large number of ferrules in parallel is constrained due to the physical structure of components in the system. This connector system has been designed for use as independent or stand-alone connectors in ANSI/VITA 48.1 (air-cooling applications) and ANSI/VITA 48.2 (conduction-cooling applications) applied to printed wiring boards (PWBs)/plug-in units defined in ANSI/VITA 46.0 VPX systems. Typical applications are in the aerospace and defense industry and include use in adverse environments for Embedded Computing, Processing, Avionics and Vetronics, Radar, Secure Communications and Imaging/Targeting.
The connector system provides a high-density, blind-mate optical interconnect in a backplane/card configuration. The fiber-optic (ribbon) cable interconnect is fed through the backplane to removable systems modules using MT ferrules. The connector system consists of a backplane connector and the mating module connector which interconnects a single ferrule, accommodating up to twelve fiber paths. The backplane connector is often referred to as a “receptacle” and the mating module connector a “plug”. For purposes of the discussion herein, the terms receptacle and plug will be utilized. However, it will be understood that these are synonymous with backplane and module respectively. Furthermore, the term “connector” refers to either a receptacle or plug, unless otherwise noted.
FIG. 1 which is prior art shows an exploded view of a conventional receptacle (backplane) connector kit. The conventional receptacle (backplane) connector kit shown in FIG. 1, may be for example in accordance with the VMEbus International Trade Association (“VITA”) Standard: “ANSI/VITA 66.4 Optical Interconnect on VPX—Half Width MT Variant”. This connector system has been designed for use as independent or stand-alone connectors in ANSI/VITA 48.1 (air-cooling applications) and ANSI/VITA 48.2 (conduction-cooling applications) applied to printed wiring boards (PWBs)/plug-in units defined in ANSI/VITA 46.0 VPX systems.
Receptacle connector kit 100 further comprises receptacle shell 102, receptacle insert subassembly 116 and receptacle retainer subassembly 112.
Receptacle insert subassembly 116 further comprises insert housing 106, alignment pins 104(a) and 104(b) and retaining screws 114(a) and 114(b) corresponding respectively to alignment pins 104(a) and 104(b) and ferrule cavity 118, which will accommodate an MT ferrule 120.
Receptacle retainer subassembly 112 further comprises retainer plate 110 and captive screws 108(a)-108(b).
Retainer plate 110 is used to secure an MT ferrule 120 inside insert housing 106. Captive screws 108(a)-108(b) serve to secure retainer plate 110 of receptacle retainer subassembly 112 to receptacle insert subassembly 116. In particular, receptacle retainer subassembly 112 and receptacle insert subassembly 116, retainer plate 110 may be used to secure an MT ferrule 120.
Alignment pins 104(a) and 104(b) serve to align receptacle insert subassembly 116 and in particular insert housing 106 to facilitate efficient fiber mating. Captive screws 108(a)-108(b) also serve to align receptacle retainer subassembly 112 to receptacle insert subassembly 116, which is important for fiber mating. Retaining screws 114(a) and 114(b) serve to couple respective alignment pins 104(a)-104(b) to insert housing 106. Thus, alignment pins 104(a) and 104(b) must exhibit a minimum diameter to accommodate retaining screws 114(a) and 114(b). The required minimum diameters of alignment pins 104(a) and 104(b) and retaining screws 114(a) and 114(b) consumes space and therefore limits the capacity of receptacle (backplane) connector kit 100 to accommodate additional MT ferrules.
FIG. 1, which is prior art, also shows how an MT ferrule may be coupled to a conventional receptacle connector kit 100. In particular MT ferrule 120, which is coupled to cable assembly 122, is inserted into ferrule cavity 118 in receptacle insert subassembly 116. Receptacle retainer subassembly 112 and receptacle insert subassembly 116, retainer plate 110 may then be used to sandwich MT ferrule 120.
Applicants have identified significant shortcomings with conventional approaches for connecting fiber-optic cables and MT ferrules in particular. In this regard, with the existing VITA 66.1 and 66.4 industry-standard plug (daughtercard/module) connectors, it can be difficult or time consuming to remove or replace the installed MT ferrule(s). Current designs require either removing the connector from the board or removing a retainer plate, which may not be accessible. Removing an MT ferrule may be necessary if the ferrule mating face cannot readily be cleaned, or if the ferrule or terminated fiber optic cable assembly becomes damaged.
Similarly, the existing mating receptacle (backplane) connectors require accessibility behind the opposite side of the board to remove and replace installed MT ferrules. The standardized alignment pins (i.e., 104) of the existing VITA 66.1 and 66.4 connectors are oversize relative to the amount of blind-mating misalignment capability they provide. These oversize pins (and the respective mating cavities) may limit the number of MT ferrules the connectors can accommodate. The existing VITA 66.1 and 66.4 industry-standard connectors are spring-supported only within the plug connector. This may result in diminished optical performance including return loss compared to MTP/MPO connectors containing springs in both halves. In particular, MT ferrules having more than one row of physical-contact fibers (e.g., 2-row, 24-fiber ferrules) installed have a pronounced risk of poor or inconsistent return loss performance. The alternative is to restrict usage to single-row MT ferrules (typically 12 mating fibers) or lensed MT ferrules.